  const PI = 3.14159265358979324;
  function transformLat(x, y) {
    let ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x))
    ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0
    ret += (20.0 * Math.sin(y * PI) + 40.0 * Math.sin(y / 3.0 * PI)) * 2.0 / 3.0
    ret += (160.0 * Math.sin(y / 12.0 * PI) + 320 * Math.sin(y * PI / 30.0)) * 2.0 / 3.0
    return ret
  }
  function transformLon(x, y) {
    let ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x))
    ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0
    ret += (20.0 * Math.sin(x * PI) + 40.0 * Math.sin(x / 3.0 * PI)) * 2.0 / 3.0
    ret += (150.0 * Math.sin(x / 12.0 * PI) + 300.0 * Math.sin(x / 30.0 * PI)) * 2.0 / 3.0
    return ret
  }

  export default class transformGCJ2WGS{
    constructor(gcjLat, gcjLon){
      this.gcjLat = gcjLat
      this.gcjLon = gcjLon
    }

    init(){
      let a = 6378245.0 //  a: 卫星椭球坐标投影到平面地图坐标系的投影因子。
      let ee = 0.00669342162296594323 //  ee: 椭球的偏心率。
      let dLat = transformLat(this.gcjLon - 105.0, this.gcjLat - 35.0)
      let dLon = transformLon(this.gcjLon - 105.0, this.gcjLat - 35.0)
      let radLat = this.gcjLat / 180.0 * PI
      let magic = Math.sin(radLat)
      magic = 1 - ee * magic * magic
      let sqrtMagic = Math.sqrt(magic)
      dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * PI)
      dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * PI)
      return {
        'lat': this.gcjLat - dLat,
        'lng': this.gcjLon - dLon
      }
    }
  }